Subsea fiber optical communications systems need routine monitoring to guarantee their performance and minimize potential loss of service by detecting and solving wet plant faults and possibly aggressive threats at an early stage. Currently established monitoring technologies include the use of line monitoring systems (LMS) to detect signal peaks looped back from each undersea repeater and terminal with high loss loopback (HLLB) technology.
When there is a change in performance along the optical path, the amplitudes of these loopback signals change in the repeaters surrounding the fault location. The changes present distinct patterns which may be utilized to identify fault conditions. Such fault conditions include, for example, changes in fiber span loss, changes in optical amplifier pump laser output power, and fiber breaks. Some approaches to recognizing fault conditions based on a corresponding fault signature include utilizing automatic signature analysis (ASA). Existing ASA-based fault analysis can detect relatively large changes in the transmission system, but often lack accuracy to report small changes that may indicate degraded performance of a particular element over time.
Some undersea transmission systems utilize repeaters with Command-Response (CR) features that allow for operational parameters such as output power and input power to be queried directly from each repeater. However, Command-Response requires specialized hardware within each repeater that can significantly increase unit costs and reduce operational lifespan, which is particularly problematic in an undersea environment that makes repairs impractical.